One time I drove up to somebody who was in passive mode, and started drinking all of my beers. He did the same, and we were both stumbling around and I started shooting different guns into the air, doing different player actions and stufff, basically acting like I was just being friendly and making my character do funny stuff. I even set myself on fire while drunk, died and came back. He was in passive mode the whole time.
We did this for like 10 minutes, then I got in my car (which was set to passenger access only), a Roosevelt, and started honking that funny horn it has. He got in the passenger seat. That was the mistake that sealed his fate. I got out of the car and calmly walked to the front while drinking a cola, pulled out my minigun and blasted him and kept shooting until he respawned, got back in my car and drove by him really fast while honking that troll horn. The last he saw of me was me driving by way too fast for him to react, while going "aahoooooo" with my car horn.
edit: actually that probably wasn't my most evil deed, my worst one was probably when I found a level 5 who had ran out of bullets in the countryside. I just kept messing with him and there was nothing he could do about it. Not very kind of me to say the least, but it was hilarious. I also offered him a couple of cars so that he could get away, but all of them were rigged with sticky bombs.